A power conversion device for performing step-up and step-down operations between a motor and a power supply is employed as one of parts of a vehicle, such as a hybrid car or an electric car, which utilizes the motor as a driving source or as a power generation source in regeneration. The power conversion device includes a converter for changing the magnitude of electric power.
As an example of the vehicle-loaded converter, there is a two-way DC-DC converter (Patent Literature (PTL) 1, FIG. 6). One component of the converter is a reactor for smoothing a current that is generated with ON/OFF switching operations of a switching device.
As illustrated in FIG. 14, a reactor 1000 typically includes an annular magnetic core 100 made of a magnetic material, and a coil 110 having a pair of coil elements 110a and 110b, which are each formed by winding a wire 110w and which are arranged around respective parts of the magnetic core 100 (PTL 1, FIG. 1). The magnetic core 100 is constructed in an annular shape by combining a pair of inner core portions (not illustrated), which are inserted respectively into the coil elements 110a and 110b, and a pair of outer cores 100e, which are arranged in sandwiching relation to the inner core portions arranged in parallel. The reactor 1000 is placed in, e.g., a case (not illustrated) and is encapsulated with a potting resin (PTL 1, FIG. 3). When the reactor is used, the case is fixed to a cooling base.
Further, PTL 2 discloses a reactor including a magnetic core, generally called a pot type core, which includes a columnar core disposed inside one cylindrical coil, a cylindrical core disposed to cover an outer periphery of the coil, and a pair of disk-shaped cores disposed respectively at end surfaces of the coil, the magnetic core covering substantially the entire outer periphery of the coil (PTL 2, FIGS. 1 and 2). In the pot type core, the columnar core and the cylindrical core, both concentrically arranged, are coupled to each other, thereby forming a closed magnetic path.
A resonance-type DC-DC converter capable of performing soft switching with a smaller switching loss than that in known converters (PTL 3) has been studied in recent years. Such a converter includes an auxiliary circuit including a reactor and a switching device both for resonance, in addition to a reactor for smoothing. PTL 3 discloses an arrangement including an inductor L1, an inductor L2, and an inductor Lr having an inductance value smaller than those of both the inductors L1 and L2 (PTL 3, FIG. 1). The inductor L1 functions as the reactor for smoothing, and the inductors L2 and Lr realize the soft switching.